Component assembly and method for producing the same

ABSTRACT

In a component assembly and method for producing the same, the component assembly includes at least one component arranged on a support subframe, e.g., a printed circuit board. An insulator enclosing the component and including two isolating superimposed layers is also arranged on the support substrate. A sealing mass covering the component is arranged inside the insulator. The two or more isolating layers are made from the same isolating material and connected at the contact area.

FIELD OF THE INVENTION

The present invention relates to a component assembly as well as to amethod for producing a component assembly.

BACKGROUND INFORMATION

Electronic and/or optoelectronic components may be placed on carriersubstrates, such as circuit boards in several ways. It is customary, forinstance, for unhoused components to be initially placed on the circuitboard at a designated location and subsequently electrically contacted,for example by wire bonding. An injection needle or a so-calleddispenser is subsequently used to position an enclosed dam on thecircuit board to surround the component. Finally, in a further processstep, a suitable encapsulating material is introduced into thewell-shaped inner region of the dam, so that the component and anyexisting bonding wires, etc., are covered by the encapsulated materialand protected from environmental influences. In connection withcomponent assemblies of this kind, reference is made, for example, toGerman Published Patent Application No. 195 30 878 and JapanesePublished Patent Application No. 61-101054. From both documents it canbe inferred, that the dam has two dam layers.

A number of problems arise in the context of high component densities,as well as with regard to the use of electronic components. Thus, incomponent assemblies of this kind, a smallest possible base area must beensured for the dam on the particular carrier substrate, in order not toneedlessly cover essential space on the carrier substrate. A two-partdam structure discussed in German Published Patent Application No. 19530 878 requires, for example, a relatively large base area for the damon the carrier substrate, and therefore, does not fulfill thisrequirement.

In addition, the use of optoelectronic components requires that theencapsulating material placed over this component have, to the extentpossible, no undesired optical effect for the beam of rays passingthrough. This is also not ensured in the case of German Published PatentApplication No. 195 30 878, since the beam of rays passing through isdeflected at the curved boundary surface between the encapsulatingmaterial and the ambient air due to the resulting lens effect.

It is also to be noted in connection with the assembly described inJapanese Published Patent Application No. 61-101054 that the two damlayers having different melting points require considerable costs forprocess control due to the different processing temperatures. Expensesare also entailed in terms of process technology, due to the necessityto process a plurality of dam materials in the manufacturing of such anassembly.

SUMMARY

An object of the present invention is, therefore, to provide a methodfor the manufacture of a component assembly which satisfy the specificrequirements. In particular, besides a greatest possible componentdensity and adequate mechanical stability, an object of the presentinvention is to also ensure the usability of optoelectronic components.Also desirable is a simplest possible manufacturing of a componentassembly of this kind.

This objective is achieved by providing a method as described herein.

The measures in accordance with the present invention may ensure that astable bond forms in the contact region between adjacent dam layers.When a suitable dam material is used, there is a stable cross-linking ofthe two adjacent dam layers in this region. The stable bond in thisregion results in a mechanically more resistant overall assembly. It isthereby possible to form high dams having a comparatively small damsurface area, i.e., high component densities are also able to beultimately realized in accordance with the present invention. Due to thepossible high dam structure, the inner region of the dam may be filledwith a suitable encapsulating material such that this material has avirtually ideal, plane surface area. No undesired, optically deflectingaction results at the boundary surface with the ambient air for the beamof rays passing through. As discussed above, this may be an essentialrequirement when optoelectronic components are to be used in assembliesof this kind.

The use of the identical dam material in all dam layers also signifiesthat all dam layers have the same thermal expansion coefficient.Therefore, no thermally induced stresses may occur between the variousdam layers in the dam.

Also, from a standpoint of production engineering, a number ofadvantages may be derived from the measures according to the presentinvention. Thus, in contrast to the above-mentioned Japanese PublishedPatent Application No. 61-101054, the need is eliminated to keepdifferent materials available for the minimum of two dam layers, sincethe at least two dam layers are made of the same material. In addition,in the various process steps in which the various dam layers areapplied, there is no longer a need to have different temperatures due todifferent melting points or processing temperatures.

Due to the use of the same material in the dam layers, a stable bond maybe ensured. Thus, for instance, when using suitable material, a chemicalcross-linking results in the contact region upon final curing. Theresult is a high mechanical load-bearing capacity of the dam.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a lateral cross-sectional view of an exemplary embodiment ofthe component assembly according to the present invention.

FIG. 2 is a plan view of the component assembly illustrated in FIG. 1.

FIG. 3 is an enlarged view of the dam illustrated in FIG. 1.

FIGS. 4a-4 d illustrate various process steps of one example embodimentof the method according to the present invention.

DETAILED DESCRIPTION

In schematic form, FIG. 1 is a cross-sectional view of an exampleembodiment of the component assembly according to the present invention.For example, the depicted view may be a detail of a carrier substrate 10configured as a circuit board, upon which other component assemblies ofthis kind are also provided.

In the illustrated exemplary embodiment, carrier substrate 10 isdesigned as a circuit board and functions as a carrier element for thecomponent assembly. As a suitable material for carrier substrate 10,conventional circuit-board material is provided, such as FR4 or FR5.Alternatively hereto, a differently configured carrier substrate 10 mayalso be used, such as suitable ceramic, e.g., Al₂O₃. Electricalconductor tracks may extend in the carrier substrate 10 as an example.They may be used for the contacting of the unhoused electronic component20, as well as of the other components on circuit board 10. The presentexample embodiment provides for a contacting of component 20 usingbonding wires 21 a, 21 b. Bonding wires 21 a, 21 b electroconductivelyconnect component 20 to the conductor tracks in carrier substrate 10. Analternative and/or additional electrical contacting of component 20 maybe possible, such as a so-called narrow-ribbon contacting, or also theuse of soldered connectors.

In this example embodiment, component 20 is designed as anoptoelectronic component or as a so-called OPTO-ASIC. In addition tooptoelectronic components, such as photodiodes, it includes otherelectronic components for signal processing. The present invention mayalso be implemented in conjunction with conventional electroniccomponents, such as ASICs, etc.

The particular component 20 is placed on carrier substrate 10, which maybe done by bonding to carrier substrate 10. Soldering or alloying isalso alternatively possible. The present invention may be suited in thiscase for assembling unhoused electronic and/or optoelectronic componentson circuit boards, i.e., components which do not have their own housingand, accordingly, offer a particularly space-saving design.

Furthermore, the component assembly according to the present inventionincludes a dam 30, which is placed on carrier substrate 10 and surroundsor encircles the particular component 20. From the plan view of thecomponent assembly illustrated in FIG. 2, dam 30 surrounds component 20quadratically. Alternative geometries are also possible with respect tothe shape of surrounding dam 30, e.g., rectangular, polygonal, or rounddam profiles, etc.

A first function of dam 30, with respect to the component assemblyaccording to the present invention, is to form a boundary of the surfacerequired for embedding component 20 using an encapsulating compound 40on carrier substrate 10. Once dam 30 is created, encapsulating compound40 is introduced into the well-shaped inner region of surrounding dam30. The purpose of embedding using encapsulating compound 40 is toprotect component 20 from mechanical influences. In this connection,because of optoelectronic component 20, a transparent and low-viscosityencapsulating compound 40, such as unfilled epoxy resin, is used in thedescribed exemplary embodiment. In the inner region of dam 30,encapsulating compound 40 covers component 20, including bonding wires21 a, 21 b, so that, once encapsulating compound 40 is cured, theseelements are reliably protected. To fulfill this purpose, encapsulatingcompound 40 may completely cover the elements to be protected, i.e., inthis example embodiment, also bonding wires 21 a, 21 b in particular,for which a specific level of encapsulating compound 40 to be applied,may be required. Since this compound, when applied using an injectionneedle, is not yet cured and flows out, dam 30 ultimately is used toadjust the necessary level of encapsulating compound 40, withoutcovering unnecessary surface area on carrier substrate 20.

Alternatively to the illustrated exemplary embodiment, bonding wires 21a, 21 b may not be fully covered with encapsulating compound 40, rather,for the most part, merely surrounded by the same.

When no optoelectronic components are provided in the component assemblyaccording to the present invention, a non-transparent encapsulatingcompound 40 may also be used. A black encapsulating compound 40 may beused which protects the particular electronic component 20 from unwantedirradiation.

The component may be covered using encapsulating compound, for examplewhen contacting using bonding wires are not provided and, accordingly,there would also be no bonding wires to protect.

Another function of dam 30, specifically when using optoelectroniccomponents, is that, virtually ideal plane boundary surfaces are able tobe ensured, between encapsulating compound 40 and the neighboring air.The result is that there is no undesired deflection of incident or, asthe case may be, emergent beams of rays at this boundary surface 41.

Dam 30 enables a defined, i.e., reproducible height h of the componentassembly to be reliably set over carrier substrate 10 in the course ofmanufacturing. This may be especially significant when an assembly ofthis type is used, for example, under narrowed, spatial conditions. If,for instance, a component assembly of this type is used on the scanningplate of an optical position transducer disposed oppositely to arotating partial disk, a relatively small distance is provided betweenthe scanning plate and the partial disk in compact systems. On noaccount, then, may any accessories mounted on the side of the scanningplate exceed a specific, predefined height.

In the illustrated exemplary embodiment of the present invention, dam 30is composed of two dam layers 31, 32, which are placed one over theother and are made of the same dam material. There is a bonding betweenthe two adjoining dam layers 31, 32, in their contact region.Alternatively to a configuration including two dam layers 31, 32, a damconfiguration may also be provided which includes more than two such damlayers 31, 32, each of the same dam material, if an even greater heighth of dam 30 were necessary.

A highly viscous encapsulating compound, such as filled epoxy resin or asilicon, is a suitable dam material, for example. Within the scope ofthe present invention, a dam material for the various layers 31, 32 ofdam 30 is selected, which allows a cross-linking of the same and, thus,a stable bonding in the contact region of adjoining dam layers 31, 32.

In the case of other dam materials, a mechanical engagement of the roughsurfaces of the dam layers may be present in this contact region, forexample. Depending on the material selection, other connectionmechanisms may be optionally present in the contact region between thedam layers.

By constructing dam 30 out of two or more dam layers 31, 32 from thesame dam material, in accordance with the present invention, a definedadjustment of the desired ratio V of dam height h and dam width b(V=h/b) is able to be made. By applying measures described below, widthb of dam 30 is set in defined fashion, without any undesired flowing ofthe dam material and, thus, unwanted enlargement of the required carriersubstrate surface taking place. By subsequently applying one or morefurther dam layers 32 to first dam layer 31, the requisite dam height his then able to be set in definable, i.e., reproducible fashion. Theratio V=h/b may be in the range of 0.5<V<1 as an example. However, onthe basis of an appropriate process control, other ratios V may also befundamentally adjusted.

Typical values for resulting dam height h and dam width b are h=0.8 mmand b=1.0 mm.

FIG. 3 is an enlarged view of dam 30 of FIG. 1, which includes the twodam layers 31, 32. Besides the geometric dimensions, dam height h anddam width b, FIG. 3 also illustrates contact region 33 adjoining damlayers 31, 32, where there is a cross-linking of the two dam layers 31,32 and, thus, a stable bonding of the same.

As illustrated in FIGS. 4a-4 d, one example embodiment of the methodaccording to the present invention is presented for manufacturing acomponent assembly as described in FIGS. 1-3.

In a first process step illustrated in FIG. 4a, unhoused component 20 isplaced on carrier substrate 10 or the circuit board and, if indicated,bonded thereto. Component 20 is then electrically contacted, which maytake place via wire bonding and the placement of corresponding bondingwires 21 a, 21 b.

First dam layer 31 is subsequently applied to carrier substrate 10,which, as explained above, completely surrounds component 20.

The corresponding process step is illustrated in FIG. 4b. Theappropriate dam material is applied by a schematically indicatedinjection needle 50 using so-called dispensing technology. Duringapplication of first dam layer 31, carrier substrate 10 is heated totemperature T, which is illustrated by schematically indicated heatingdevice 60. The heating of the circuit board or, if indicated, of analternative carrier substrate 10 effects a precuring of the dam materialof first dam layer 31, immediately upon making contact on carriersubstrate 10. This makes it possible to prevent first dam layer 31 fromflowing in unwanted fashion, and from consuming surface area. It is,therefore, possible to adjust desired dam width b in a defined manner.The desired width or height of first dam layer 31 is able to be set in adefined manner by adjusting the traversing rate of injection needle 50,the applied quantity of the dam material, as well as temperature T ofcarrier substrate 10.

Still during the curing of first dam layer 31, second dam layer 32 issubsequently applied, as illustrated in FIG. 4c, with the aid ofinjection needle 50. As explained above, for second dam layer 32, thesame dam material as for first dam layer 31 is used. Since a completecuring has not taken place in the top part of first dam layer 31,following application of second dam layer 32 in the contact region, across-linking of the two dam layers 31, 32 occurs, i.e., an especiallyintimate and, thus, stable bond is formed between adjoining dam layers31, 32.

Subsequently, i.e., after curing of the two dam layers 31, 32, asillustrated in FIG. 4d, encapsulating compound 40 is introduced into thewell-shaped inner region of dam 30, which is accomplished using aninjection needle 70. For this, it is customary in the correspondingdevice to use a different injection needle 60 than the one used in thepreceding process steps. In this connection, the amount of encapsulatingcompound 40 introduced is enough to fill the inner region of the damnearly to the upper edge of dam 30, i.e., to the upper edge of top-mostdam layer 32. Upon curing of encapsulating compound 40, the result is acomponent assembly which is protected from mechanical influences.

Alternatively, it may also be provided to begin introducingencapsulating compound 40, immediately following the application of lastdam layer 32.

Within the framework of the present invention, there are alternativevariants in addition to the described example embodiments.

What is claimed is:
 1. A method for manufacturing a component assemblyon a carrier substrate following placement of a component on the carriersubstrate, comprising: applying an enclosed dam including two superposeddam layers to the carrier substrate surrounding the component,including: initially applying a first dam layer of a dam material;subsequently applying a second dam layer of identical dam material overthe first dam layer, in a contact region of the two dam layers, abonding resulting between the first dam layer and the second dam layer;and during the applying of the first dam layer, heating the carriersubstrate effecting a precuring of the dam material of the first damlayer immediately when contact is made on the carrier substrate.
 2. Themethod according to claim 1, wherein the condition 0.5<h/b<1 issatisfied, b representing a dam width and h representing a dam height.3. The method according to claim 1, wherein the bonding between thefirst dam layer and the second dam layer includes cross-linking of thefirst dam layer and the second dam layer.
 4. The method according toclaim 1, wherein the dam material includes a filled epoxy resin.
 5. Themethod according to claim 1, wherein the component includes anoptoelectronic component.
 6. The method according to claim 1, whereinthe carrier substrate includes a circuit board.
 7. The method accordingto claim 1, wherein the second dam layer is applied in the second damlayer applying step as soon as the first dam layer begins to cure in anarea of the carrier substrate but is not yet fully cured in the contactregion of the dam layers.
 8. The method according to claim 1, furthercomprising electroconductively connecting the component to conductortracks in the carrier substrate prior to the applying step.
 9. Themethod according to claim 1, further comprising introducing anencapsulating compound in an inner region of the dam to cover thecomponent subsequent to a curing of the applied dam layers.
 10. Themethod according to claim 1, further comprising introducing anencapsulating compound in an inner region of the dam to cover thecomponent subsequent to the application of the second dam layer.
 11. Themethod according to claim 1, further comprising introducing a quantityof encapsulating compound into an inner region of the dam to fill thedam nearly to an upper edge of the dam.
 12. The method according toclaim 1, further comprising introducing a quantity of encapsulatingcompound into an inner region of the dam to fill the dam to an upperedge of a top-most dam layer.
 13. The method according to claim 7,wherein the dam layers are applied in the applying step using aninjection needle.
 14. The method according to in claim 13, furthercomprising adjusting at least one of a traversing rate of the injectionneedle, an applied quantity of the dam material, and a temperature ofthe carrier substrate to one another to set a height and a width of thedam layers.
 15. The method according to claim 8, wherein the componentis electroconductively connected in the connecting step by bonding wiresto the conductor tracks in the carrier substrate.
 16. The methodaccording to claim 9, wherein the encapsulating compound is transparent.17. The method according to claim 10, wherein the encapsulating compoundis transparent.
 18. The method according to claim 11, wherein theencapsulating compound is transparent.
 19. The method according to claim12, wherein the encapsulating compound is transparent.
 20. A device formanufacturing a component assembly on a carrier substrate followingplacement of a component on the carrier substrate, comprising: a deviceconfigured to apply an enclosed dam including two superposed dam layersto the carrier substrate surrounding the component, including: anarrangement configured to initially apply a first dam layer of a dammaterial; an arrangement configured to subsequently apply a second damlayer of identical dam material over the first dam layer, in a contactregion of the two dam layers, a bonding resulting between the first damlayer and the second dam layer; and an arrangement configured to heatthe carrier substrate, during application of the first dam layer, toeffect a precure of the dam material of the first dam layer immediatelywhen contact is made on the carrier substrate.